\beginsection{7.1}

Write out the first five terms of the following sequences.

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(a) $s_n=1/(3n+1)$
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$s_1={1\over4}$,
$s_2={1\over7}$,
$s_3={1\over10}$,
$s_4={1\over13}$,
$s_5={1\over16}$

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(b) $b_n=(3n+1)/(4n-1)$
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$b_1={4\over3}$,
$b_2={7\over7}$,
$b_3={10\over11}$,
$b_4={13\over15}$,
$b_5={16\over19}$

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(c) $c_n=n/3^n$
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$c_1={1\over3}$,
$c_2={2\over9}$,
$c_3={3\over27}$,
$c_4={4\over81}$,
$c_5={5\over243}$

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(d) $\sin(n\pi/4)$
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$\sqrt2\over2$,
$1$,
$\sqrt2\over2$,
$0$,
$-{\sqrt2\over2}$
